On Wed, Sep 12, 2007 at 11:23:20AM -0400, Jaime Pozo wrote:
> Hello,
> 
> When i use Axis lathe in mm (LINEAR_UNITS = mm & Display in mm),
> the "extents" draw in the backplot are wrong when i use tool offsets.
> (all tool table data are in mm)
> it seems  take the tool offsets  in "inch" and multiply by 25.4(inch-to-mm).
> I try to modify Axis but i don?t find where.
> 
> Something similar occurs in the tool cone drawing, but i solve it modifing
> lathetool() in axis
> 
> I hope someone can help me,
> 

Hi Jaime,

In EMC versions earlier than the soon-to-be-released 2.2.0, there are
problems with the units in the tool table.  The numbers in there are
"unitless" so, for instance, if you have a 20mm diameter tool and you
load it while in G21 mode it is 20mm, but if loaded in G20 mode it is
20 inches!  This behavior is explicitly spelled out in the RS274NGC
spec.  This is one of the ways the EMC2 team has decided to diverge
from the spec.  These divergences are documented here:

http://www.linuxcnc.org/docs/devel/html/gcode/main/index.html#SECTION00910000000000000000

In the upcoming 2.2 versions, these problems are fixed, so you can
describe a tool once in the tool table and use it in metric and inch
gcode programs as you please.  Since AXIS now knows the size of the
tool, it can also display it correctly (previously it could not
determine the size of the tool, since the numbers were unitless and
it could not guess which G20/G21 mode you intended to use with a
particular tool.)

I hope this is at least somewhat clear.  It is a complex issue but
be assured it is now fixed.  If you do not want to wait for a 2.2.0
release you could compile and run the development code.  That
procedure is documented here:

http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Installing_EMC2#On_Ubuntu_5_10_and_6_06_from_source

Chris


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